This invention relates to a metal machining device with control circuit isolation.
Machining devices for cutting or joining large metal workpieces often are constructed to provide a pair of gantries mounted for movement along longitudinal rails, and a transverse elongated metal bridge extending between the gantries. The bridge is constructed to carry one or more carriages which in turn carry machining tools, such as welding heads or cutting torches.
In recent years, the primary control for gantry, carriage and tool movement and operation has been a so-called CNC (computerized numerical control) unit which has been fixedly mounted adjacent one end of the bridge, as for example in one of the gantries. The CNC unit includes a programmable computer and numerous primary electronic circuits which are responsive to a power input and which provide various outputs to operate the machine.
Both the power input and the various outputs include supplemental electronic circuits. The present practice has been to dispose many of these supplemental circuits in separate thin-walled box-like housings which are mounted to the exterior of the bridge and gantries, wherever there is room to put them. The connecting electronic cables have formed, together with the torch or welding head supply systems, an exposed spaghetti-like network of connecting elements which can be positioned differently each time and which, through proximity, can become electrically coupled and/or act as antennas which receive the noise and transmit the undesirable signals back to the CNC.
At least some of the supplemental circuits create radiating electronic noise which, it has been found, can undesirably interfere with the proper operation of the computer of the CNC unit.
It is a task of the invention to reduce the aforementioned problems.
In accordance with the various aspects of the invention, the transverse tool-carrying bridge is formed as a generally hollow heavy-walled closed box-beam which has mounted therein at least part of the supplemental electronic circuitry. A beam side-wall is provided with a plurality of doors which open to permit access to a plurality of circuit-holding drawers. When the doors are closed, the bridge forms a unitary hollow housing containing the supplemental electronic circuitry which serves to mechanically and electronically isolate them and substantially reduce the radiation of electronic noise therefrom to the computer. The removal and harness-like fixing of at least some of the connecting electronic cables to within the bridge serves to reduce the problems of electronic coupling and other interference. Further improvement in isolating is accomplished by placing progressively noisier supplemental circuits in drawers which are progressively farther away from the computer.